We examine the origin and behavior of the catastrophic tsunami that impacted Skagway Harbor at the head of Taiya Inlet, Alaska, on November 3, 1994. Geomorphologic and tide gauge data, combined with numerical simulation of the event, reveal that the tsunami was generated by an underwater land-slide formed during the collapse of a cruise-ship dock undergoing construction. Use of a fine-grid model for Skagway Harbor and a coarse-grid model for Taiya Inlet enables us to explain many of the eyewitness accounts and to reproduce the dominant oscillations in the tide gauge record, including the persistent (~1 h) 3-min oscillation in Skagway Harbor. The occurrence of the landslide is linked to critical overloading of the slope materials at a time of extreme low tide. ¿ 1999 American Geophysical Union